1. Field of the Invention
This invention relates to an improved metering discharge device for particulate material, such as grain, and is a continuation-in-part of application Ser. No. 729,730 filed Oct. 5, 1976 (now abandoned).
2. Summary of the Prior Art
Damp grain, such as corn, rice, wheat, beans, etc. is frequently dried by means of heated air in a drying column or tower. Such a drying column or tower normally includes a grain reservoir having a grain inlet at the top and a grain outlet at the bottom and being adapted to have the grain pass through in a confined mass. It also includes spaced orifices communicating with the interior of the reservoir and each adapted to either serve as an air inlet or outlet with means for circulating air between the orifices and through the mass of grain.
A popular type of dryer is the concurrent-counter-current flow grain dryer in which hot drying air travels downwardly in the same direction as the flowing grain and a counter-current flow of cooling air travels in an opposite direction to the direction of grain travel. With this system, air exhaust means are provided intermediate the hot air inlet and cooling air inlet.
With drying systems of the above type, the movement of the mass of grain down the drying column must be very carefully controlled and in the past this has been done by means of metering rolls in a bottom portion of the dryer, such as those illustrated in Rathbun, U.S. Pat. No. 3,710,449 issued Jan. 16, 1973. The rolls shown in this patent are typical of those used in the grain drying industry and are in the form of a shaft with a series of radially extending paddles or blades which pass the grain through gaps in the floor of the dryer. These metering rolls must be particularly designed for the purpose and are expensive to construct. Moreover, because of the long support span of each roll, it is difficult to prevent some sagging which results in unequal rates of grain flow in different metering rolls and in different portions of each metering roll. This is, of course, highly undesirable in terms of obtaining a smooth, uniform travel of the mass of grain down through the dryer, whereby uniform drying is achieved.
It is, therefore, the purpose of the present invention to provide an improved design of metering means for grain dryers which will overcome the construction difficulties as well as the operating difficulties encountered with the previous metering rolls.
In accordance with the present invention there is provided a device for the metered discharge of grain at a controlled rate from a drying tower containing this grain. The discharge device comprises a discharge floor structure for a grain drying tower, said floor structure comprising a horizontal floor member having a plurality of substantially uniformly spaced apertures of substantially uniform transverse dimensions, said apertures being arranged in a plurality of straight rows having a plurality of apertures in each row, a tube member extending downwardly beneath each said aperture, each said tube member having a bottom end closure and a pair of opposed circular openings in the side walls thereof with the side wall openings in all tubes in each row being in axial alignment, a cylindrical sleeve mounted in each said circular opening and a rotatable auger extending axially through each row of sleeves. Also extending across the drying tower immediately above said discharge floor structure for operative co-operation therewith are a plurality of laterally spaced, inverted channel members with open bottoms for distributing cooling air into the grain in the tower. The channel members in this position prevent any problems of substantial quantites of dust and chaff from the grain tending to collect in the tube members and augers.
Since there can be quite close tolerances between the flight of the auger and the periphery of the openings, it will be seen that flow of grain out of the vessel can be stopped and started with great accuracy and the rate of flow can also be controlled with great accuracy. Moreover, since the auger is supported by each tube, it will be seen that if all augers in a dryer are rotated at a uniform speed, the particulate material will emerge at an absolutely uniform rate from all tubes. Furthermore, with the augers simply resting within the tube side wall openings, no cumbersome support hangers, etc. are required.
For a large commercial dryer, the tubes are normally arranged in parallel rows with a single auger extending laterally through all tubes in each row. In this way the tubes can be substantially uniformly spaced across the entire bottom of the dryer.
The location and design of the cooling air delivery channels are also important features of this invention. Thus, the dryer can be used for the direct drying of grain as harvested without any precleaning, with the result that considerable amounts of chaff, dust, etc. are contained in the grain. It has been found in certain designs of dryers that considerable amounts of this dust and chaff tends to accumulate within the discharge floor tubes and thereby interfer with the uniform discharge of grain through the augers. Of course, in order to have a uniform drying of the grain in the tower, the columnar mass of grain must move down through the tower in a uniform manner and this means that all of the augers of the discharge floor must discharge the grain at a uniform rate.
Thus, according to one of the features of this invention, by using cooling air delivery channels in the form of inverted members with open bottoms extending across the drying tower immediately above the discharge floor structure, the problem of dust and chaff tending to collect in the tubes and augers was avoided. It appears that with this particular configuration, the air emerges from the bottoms of the channel members in a generally downward direction and then loops upwardly towards the discharge floor. However, because of the initial downward movement of the cooling air from beneath the channels, some of this downwardly moving air is directed into the tubes and this air movement has the effect of carrying downwardly any light chaff, dust, etc. which might have a tendency to collect in those locations. It has been found that this slight entrainment of air is sufficient to eliminate the problem of chaff and dust accumulation.